The present invention relates to construction equipment, such as cranes, having an upper works rotatably mounted on a lower works, and more particularly to an apparatus for permitting a quick separation and assembly of the lower works and upper works.
The problem addressed by the present invention is described in an article entitled "Solving The Quick-Disconnect Problem For Big Bearings" in the Jul. 7, 1983 issue of Machine Design.
Construction equipment, such as cranes or excavators, often must be moved from one job site to another. Moving a crane or excavator can be a formidable task when the machine is large and heavy. For example, highway limits on vehicle-axle loads must be observed and overhead obstacles can dictate long, inconvenient routings to a job site.
One solution to improving the mobility of large construction machines is to disassemble them into smaller, more easily handled components. For example, the upper rotating structure of a crane with a large-diameter, swing bearing can be removed from the mobile lower works. Because most swing bearings have at least one bolted interface, the machine can be taken down into more manageable sections for transport.
The disassembly of a crane with a conventional bearing having an inner race and an outer race is both labor-intensive and time-consuming, making it a costly undertaking. The disassembly of numerous high-strength fasteners is one factor that impedes rapid undecking of machines As an example, a 200-ton lifting crane with a 100-in. (pitch-diameter) swing bearing may have 70 or more bolts in one or both bearing rings. To disconnect and reassemble the bearing, all the bolts in one of the bearing rings must be disassembled, replaced, and uniformly torqued to a high preload.
Machine disassembly can cause alignment difficulties as well. For instance, the bearing bolt holes must be aligned precisely with mounting-surface holes in the reassembly of a machine. Because the machine parts are large and heavy, such alignments can be unwieldy and time-consuming. Moreover, if the disconnect is made at the outer bearing ring (most often the ring fixed to the machine rotating structure), then the swing bearing drive also must be critically aligned during machine assembly to minimize backlash and attendant shock loading from slewing motion.
The Machine Design article discloses a number of machine designs, many of which are patented, that have been developed to overcome these problems. For examples of previously patented approaches to solving this problem, see U.S. Pat. Nos. 4,478,340; 4,436,444; 4,248,488; 3,941,252; 3,923,407; 3,921,817; 3,726,418 and 2,965,245.
Many of the previously patented devices have the disadvantages that they are expensive. Also, the configurations are seldom interchangeable with standard bearings. Further, in many cranes, the upper works is the heaviest part of the disassembled crane, and is therefore the limiting element in the transportability of the crane. Thus, a quick disconnect system should preferably not add weight to the upper works.